評估GeneXpert MTB／RIF Assay應用於臨床偵測結核及rifampin抗藥性之效能

Evaluation of GeneXpert MTB/RIF Assay for detection accuracy of tuberculosis and rifampin resistance in clinical practice

為評估GeneXpert MTB／RIF assay應用於檢測結核菌及rifampin抗藥性之效能，本實驗將2017年6月到2019年1月間TB實驗室執行之339個臨床檢體Xpert MTB／RIF偵測數據進行回溯性統計,並將其結果與傳統抗酸菌培養與藥物敏感性試驗結果之一致性進行比較。結果顯示,339個檢體中共培養出120株（35.4％）結核菌群及5株（4.2％）多重抗藥性菌株。Xpert MTB／RIF assay測定之敏感度為95.0％（抹片陽性者98.2％，抹片陰性者60.0％）及測定之特異性為99.5％。Xpert MTB／RIF assay在rifampin抗藥性檢測之敏感性及特異性皆為100％。依據我們的研究，Xpert MTB／RIF assay在抹片陽性的肺部及肺外檢體測定上具有高度敏感性，並能成功篩除非結核型分枝桿菌。但在含菌量較少之抹片陰性檢體之測定則獲得較低的敏感性（肺部檢體為83.3％，肺外檢體為25％）。

In order to assess the diagnostic accuracy of Xpert MTB/RIF assay for tuberculosis (TB) and rifampin resistance detection, we retrospectively reviewed the examination results of the Xpert MTB/RIF assay which were performed between June 2017 and January 2019 in our mycobacteriology laboratory. A total of 339 specimens were analyzed and the results obtained by the assay were compared to culture and phenotypic drug susceptibility testing method. Of 339 specimens, 120 (35.4%) were MTBC culture positive and 5 (4.2%) were multidrug-resistant (MDR). For the detection of MTBC, Xpert MTB/RIF sensitivity was 95.0% (98.2% and 60.0% in smear-positive and -negative specimens) and specificity was 99.5%. For the detection of rifampin resistance, Xpert MTB/RIF sensitivity and specificity were 100% , respectively. According to our study, the assay showed high sensitivity in detecting MTBC in AFB smear positive pulmonary and extrapulmonary specimens and correctly excluded NTM from MTBC, but less sensitivity was found in smear-negative specimens (83. 3% and 25% in pulmonary and extrapulmonary specimens) which contained low numbers of mycobacterium bacilli.